The present invention relates to a high-frequency cutting instrument for an endoscope, to be inserted into an instrument-inserting channel of an endoscope and used for surgical operations such as endoscopic mucosal resection (EMR).
High-frequency cutting instruments are widely used today for performing surgical operations (endoscopic mucosal resection, etc.) safely and precisely. For example, in an operative procedure for the endoscopic mucosal resection, physiological saline is injected under a mucous membrane of a body part as the target of resection so as to bulge the part with the saline, and the bulged part is horizontally incised and resected at its base with a high-frequency cutting instrument for an endoscope (inserted into the endoscope). For such purposes, high-frequency cutting instruments for endoscopes, having a high-frequency electrode exposed on a lateral part of an electrically insulating flexible sheath in the vicinity of the tip of the sheath, are suitable. An example of such a high-frequency cutting instrument is disclosed in Japanese Utility Model Publication No. SHO 61-7694.
FIG. 6 is a schematic diagram showing a procedure for the endoscopic mucosal resection employing a conventional high-frequency cutting instrument for an endoscope like the one shown in the above Utility Model Publication. In the procedure, the tip of a flexible sheath 1 protruding from an instrument-inserting channel of an unshown endoscope is moved horizontally by operating the endoscope, by which a bulged part 100 is cut off at its base with a high-frequency electrode 2 placed in the vicinity of the tip of the flexible sheath 1 and energized with high-frequency current.
However, when the bulged part 100 as the target of resection is larger than the high-frequency electrode 2, the bulged part 100 can not be resected completely in one action and thus the cutting action has to be repeated many times while shifting the flexible sheath 1 a bit forward for each cut and returning it to the original position (incision starting position) after each cut.
However, the flexible sheath 1, being returned to the original position after partially cutting the bulged part 100, tends to get snagged on the bulged part 100. Therefore, the endoscope has to be operated carefully so as to return the flexible sheath I to the original position avoiding the interference by the bulged part 100 and it takes a lot of trouble for precisely setting the flexible sheath 1 at the next incision starting position.